Power factor correction device and method for operating a power factor correction device

Abstract

A power factor correction device for an AC voltage supply system includes a transformer which is interconnected, on the secondary side, to form a star point circuit and which has a secondary-side connection for each phase. A module series circuit with at least two switching modules, which are connected in series and each of which has at least four switches and a capacitor, is respectively connected between each of the secondary-side connections of the transformer and the star point of the star circuit. There is provided a transformer which is a high-leakage-reactance transformer.

The invention claimed is: 
     
       1. A power factor correction device for an AC grid system, comprising:
 a high-leakage-reactance transformer having a secondary side connected up in a star point circuit with a star point, said high-leakage-reactance transformer being configured to have a short-circuit voltage relative to a rated voltage that is at least 20% when a secondary winding is shorted; 
 said transformer having one secondary-side connection per phase; 
 a respective module series circuit connected between each of said secondary-side connections of said transformer and said star point of said star circuit, said module series circuit including at least two series-connected switching modules each having at least four switches and a capacitor. 
 
     
     
       2. The power factor correction device according to  claim 1 , wherein each said module series circuit is inductor-free. 
     
     
       3. The power factor correction device according to  claim 1 , wherein each said module series circuit is air-cored-inductor-free. 
     
     
       4. The power factor correction device according to  claim 1 , wherein said high-leakage-reactance transformer has a secondary side with a star winding forming said star point and a primary side with a delta winding forming primary-side transformer connections of said high-leakage-reactance transformer. 
     
     
       5. The power factor correction device according to  claim 4 , further comprising a switching device connected between each outer system connection of the power factor correction device and said primary-side transformer connections of said high-leakage-reactance transformer or between each of said secondary-side transformer connections and an associated said module series circuit, wherein said switching device has a series circuit with a first switch and a parallel circuit with a nonreactive resistor and a second switch connected in parallel therewith. 
     
     
       6. The power factor correction device according to  claim 5 , further comprising a control device configured:
 to leave said first and second switches in an open switch position when the power factor correction device is switched off; 
 to first close said first switch and leave said second switch open in a first sequence step when the power factor correction device is started up, and then to close said second switch in a subsequent second sequence step when the power factor correction device is started up. 
 
     
     
       7. The power factor correction device according to  claim 1 , wherein each said module series circuit has, in addition to said switching modules, an impedance connected in series with said switching modules and/or a capacitor. 
     
     
       8. The power factor correction device according to  claim 1 , wherein said high-leakage-reactance transformer and said module series circuits are physically accommodated in a room sealed from an exterior. 
     
     
       9. The power factor correction device according to  claim 8 , wherein all electrical components of the power factor correction device are physically accommodated in a single building or a single enclosure that is sealed towards the exterior. 
     
     
       10. The power factor correction device according to  claim 1 , wherein each said module series circuits includes a series resonant circuit connected in series with said switching modules, said series resonant circuit having a resonant frequency three times a system frequency or an integer multiple of three times the system frequency. 
     
     
       11. The power factor correction device according to  claim 10 , wherein at least one of said series resonant circuits comprises an inductance and a capacitor connected in series therewith or said at least one series circuit consists of said inductance and said capacitor. 
     
     
       12. The power factor correction device according to  claim 11 , wherein said inductance is an inductance having an iron core. 
     
     
       13. The power factor correction device according to  claim 1 , wherein said switching modules are H-bridge modules each with four semiconductor switching elements having a respective diode connected in parallel therewith, and a capacitor. 
     
     
       14. The power factor correction device according to  claim 1 , which comprises an impedance and/or a capacitor connected between said secondary-side star point of said high-leakage-reactance transformer and an electrical connecting point for said module series circuits. 
     
     
       15. The power factor correction device according to  claim 14 , wherein said impedance is an inductance having an iron core. 
     
     
       16. A power factor correction device for an AC grid system, comprising:
 a high-leakage-reactance transformer having a secondary side connected up in a star point circuit with a star point; 
 said transformer having one secondary-side connection per phase; 
 a respective module series circuit connected between each of said secondary-side connections of said transformer and said star point of said star circuit, said module series circuit including at least two series-connected switching modules each having at least four switches and a capacitor; and 
 secondary-side leakage inductances acting on said secondary-side connections and being influenced by leakage fields of said high-leakage-reactance transformer, and wherein each of said secondary-side leakage inductances is in series with said module series circuit connected to the respective said secondary-side connection of said transformer. 
 
     
     
       17. A power factor correction device for an AC grid system, comprising:
 a high-leakage-reactance transformer having a secondary side connected up in a star point circuit with a star point; 
 said transformer having one secondary-side connection per phase; 
 a respective module series circuit connected between each of said secondary-side connections of said transformer and said star point of said star circuit, said module series circuit including at least two series-connected switching modules each having at least four switches and a capacitor; and 
 each said module series circuit having, in addition to said switching modules, an impedance being an inductance having an iron core connected in series with said switching modules and/or a capacitor.